PHILADELPHIA (CBS) — Democrat Tom Wolfe has jumped into the lead in the primary race for governor, according to a poll out Wednesday. Meantime, Republican incumbent Tom Corbett continues a downward slide in the poll.

“Corbett has been in a tailspin here for almost a year and a half,” says Tim Malloy, Assistant Director of the Quinnipiac University Polling Institute, which has been calculating the governor’s approval rating since he took office.

Malloy says this 36% approval rating is his worst ever.

“I can’t exactly tell you why,” he says. “I can tell you he faces an extreme challenge now with eight months to go.”

Seven Democrats are vying to face Corbett in November and this poll shows York County businessman Tom Wolfe has the lead after a statewide TV campaign.

State GOP spokesman Megan Sweeney remains confident in the governor.

It’s early in the campaign season,” Sweeney says, “and the more we spread the governor’s message, we’re certainly going to be seeing that grow.”

The poll also found 70% of Pennsylvanians favor raising the minimum wage.